1. Field of the Invention
The present invention relates to a data projector for projecting an image or an electrical appliance which needs to expel heated air therefrom.
2. Description of the Related Art
In recent years, data projectors are used much as image projectors for projecting a screen of a personal computer and a video image, and furthermore, an image formed by image data stored in a memory card or the like on to a screen.
The data projector incorporates therein a small, high-luminance light source such as a metal halide lamp or an extra-high voltage mercury lamp and is configured such that a light from the light source is sequentially divided into red light, green light and blue light using a red filter, a green filter and a blue filter, which are each then concentrated on to a micromirror display device designated as a liquid crystal display device or a DMD (Digital Micromirror Device) by a lens, whereby a color image is displayed on a screen by the red, green and blue light when each light is transmitted or reflected in a certain amount towards a projection opening of the projector system by the display device.
The micromirror display device is such that microscopic mirror cells are tilted independently of others by a control signal so as to control directions of light that is reflected independently by the microscopic mirror cells so tilted in such a way that light that is made to be incident on the display device by an illuminating side optical system is divided into on-state light which is reflected by the microscopic mirror cells which are in “on” position so as to be directed towards a projection lens which makes up a projection side optical system and off-state light which is reflected by the microscopic mirror cells which are in “off” position so as to be directed towards a light absorber plate. This operation is carried out in each of micromirror display devices for red, green and blue light, and times during which the mirror cells for red light, green light and blue light are switched to the “on” position to produce on-state light are controlled so as to project a color image on to the screen.
In the data projector that is configured as has been described above, since the metal halide lamp or the extra-high voltage lamp which makes up the light source is heated to a high temperature, they need to be cooled. In Japanese Patent Unexamined Publication No. 2001-312002, a technique is proposed in which air is circulated within an optical unit of a projector using a heat pipe and a cooling fan so as to reduce the temperature of the light source. In the case where air is circulated in the interior of the optical unit like this, however, there has existed an inherent problem that when the lamp is kept on for a long period of time, the temperature inside the optical unit is increased.
In addition, there have proposed many techniques in which outside air is taken in to cool a light source. However, the light source is heated to a temperature of several hundreds degrees or near a thousand degrees, and in order to mix the exhaust air which has been heated to a high temperature as a result of cooling the light source that has been heated to the high temperature with outside air, in many cases, the heat source has to be kept away a certain distance, and to make this happen, the thickness of a housing has had to be increased or the size of the housing has had to be increased. In addition, there have been caused a defect that the highly heated exhaust air heats up exhaust vents and the vicinity thereof or wobbles a projected image in front of the projection lens.